The dots on this map represent locations where ships carrying scrap metal from Portsmouth were tracked during the last 18 months. Vessel traffic was heavier in darker areas. The graphic was created using a combination of public logs from the New Hampshire Division of Ports and Harbors and AIS vessel tracking data. The basemap was provided by Google Maps. Data was processed using CartoDB.

PORTSMOUTH — While growing up on the coast of New Hampshire, Christian Salinder developed a natural curiosity about the massive cargo ships that stop by the city's working port on a regular basis.

A Dover High School alumnus, Salinder also studied at the Massachusetts Maritime Academy, and later sailed aboard large oil tankers on the West Coast.

Living back in the Portsmouth area once again, Salinder has recently been keeping an eye on some of the cargo ships arriving to load up scrap metal.

The task has been made easier by a website called marinetraffic.com, where a network of shipping enthusiasts contribute information about the global movements of large vessels.

Salinder recently began tracking the journeys of two ships that stopped at the scrap yard in Portsmouth, hoping to find out where they would unload their cargo.

He discovered that one — the IVS Kite — traveled to Turkey, unloading cargo in a place called İskenderun, north of the Syrian border. Another ship called the Hudson Bay, which departed from the Portsmouth scrap yard this month — is also destined for İskenderun, he believes.

So Salinder began to wonder why both vessels were charting a common course, and where the scrap metal culled from around the Seacoast would ultimately wind up.

If the Hudson Bay does unload its cargo in Turkey, it will have traveled a path across the Atlantic Ocean used by numerous ships before it.

Since July 2011, all but one of the 14 carrier ships that picked up scrap metal in Portsmouth traveled to the shoreline of Turkey, or nearby it, according to a Foster's Sunday Citizen analysis of public vessel tracking data and information maintained by the New Hampshire Division of Ports and Harbors.

Turkey currently tops the list of major scrap-importing economies, followed by Korea, China, India and Egypt.

The demand is largely driven by steel production. After a decade of growth, Turkish steelmakers ramped up their production even higher in 2011, according to a recent OECD report. Production of steel from scrap grew 14 percent that year.

Turkey sources its material mainly from the European Union and the United States. An export boom has been under way in the US, and that demand for scrap has been evident in New Hampshire.

The scrap yard in Portsmouth is the only American scrap facility north of Boston, according to Geno Marconi, director of Ports and Harbors. The facility is operated by Grimmel Industries, which has a headquarters in Maine. It also operates scrap yards in Albany, N.Y., and Savannah, Georgia, Marconi said.

A spokesman for Grimmel Industries could not immediately be reached for comment Friday about the destination of ships that load scrap metal in Portsmouth.

Marconi declined to comment on the business side of the scrap operation, citing a need to maintain secrecy around proprietary information.

“It's all market driven,” he said. “There are different places that [scrap] goes to."

Bulk carrier vessels often pick up scrap in Portsmouth after first loading cargo on the upper reaches of the Hudson River, Marconi said. The ships often face limitations in New York because of shallow water, so they head north to New Hampshire to pick up more scrap, he said.

Marconi said the Hudson Bay, the ship being tracked by Salinder, started its scrap hauling journey at the Port of Albany — Rensselaer in New York. It was loaded up, then traveled to Portsmouth, where it was topped off with scrap metal.

“The cost of the ship — chartering the ship — per day is the same if it's full or it's empty,” Marconi said, discussing the economics of shipping scrap metal across the Atlantic Ocean. “Obviously, they want to fill it up.”

Another vessel that docked in Portsmouth in the last year was the Cosco Jinggangshan, a 2010-built bulk carrier operating under a Chinese flag.

A description of the ship in a recent marine safety investigation indicates the Jinggangshan is managed by Cosco Far Reaching Shipping Company, and it trades between ports in Europe, South America and United States.

According to records maintained by the riverboat pilots in the area, the Jinggangshan last visited Portsmouth to pick up scrap metal on Feb. 13, 2012. It left three days later carrying a load of 30,000 tons of scrap.

A transmitter on the ship was detected on the other side of the Atlantic Ocean 10 days later. The Jinggangshan was heading east through the Strait of Gibraltar at a speed of 17 miles per hour, according to publicly available tracking data.

The ship appears to have unloaded cargo in western Turkey, in a major steel processing zone near the city of Izmir.

The region has at least 11 iron and steel production companies, which account for 25 percent of the steel making in Turkey, according to an announcement for the 1st Aliaga Iron and Steel Event, a conference that was scheduled to take place last May.

It's a system of global trading that appears to be turning the discarded piles of scrap in New Hampshire into fodder for foreign steel mills.

In places like Turkey, products are being manufactured anew from the imported scrap and sold domestically, and around the world.

The scrap metal stored in Portsmouth is trucked there by numerous businesses in southern New Hampshire and portions of Maine.

Among them is Harding Metals in Northwood. Harding does a significant amount of business with industrial clients, such as machine shops, and also takes in scrap metal from smaller metal dealers.

The business ships some products by truck to Pennsylvania, Canada and elsewhere, but a large portion winds up at the Portsmouth yard, according to office manager Ryan Chadbourn.

“It kind of fluctuates based on pricing,” he said.

Rusty automobiles, cut metal sheets and other iron products can be taken to the yard, or transferred to Grimmel's shredder in Topsham, Maine, to be ground into a finer material.

The United States is now the leading supplier of scrap exports in the world. In a typical year, the country generates around 70 million tons of ferrous scrap, and exports in the range of 24 million or 25 million.

“This is recycling at its best,” said Donald Coker, a former Portsmouth resident and member of the Ports and Harbors Advisory Council. “This is what we ought to be doing — recycling. This is a very big business.”

However, Adam Parr, a spokesman for the Steel Manufacturers Association, a Washington, D.C., based trade group for North American steel producers, cautioned the new demand for scrap metal in Turkey has downsides in the domestic market.

“It's good and it's bad,” he said. “The economic benefits associated with melting that scrap and producing steel in the U.S. is better than just selling that scrap to the rest of the world.”